Integral lubricant return riser for refrigeration systems



J1me 1966 SATORU SHIKASHO 3,257,324

INTEGRAL LUBRICANT RETURN RISER FOR REFRIGERATION SYSTEMS Filed Dec. 16, 1964 CONDENSER Il'l lll'lll EVAPORATOR INVENTOR SATORU SHIKASHO &7

ATTORNEY United States Patent 3,257,824 INTEGRAL LUBRICANT RETURN RISER FOR REFRIGERATION SYSTEMS Satoru Shikasho, Chicago, Ill., assignor to International Telephone and Telegraph Corporation, a corporation of Maryland Filed Dec. 16, 1964, Ser. No. 418,795 8 Claims. (Cl. 62-468) This invention relates generally to refrigeration systems, and has particular reference to an integral lubricant return riser for increasing the velocity of the refrigerant at reduced refrigeration loads for the purpose of lifting entrained lubricant vertically up the riser and returning the same to the compressor.

In refrigeration systems comprising a compressor, condenser and evaporator, the lubricant for the compressor becomes entrained or occluded with the gaseous refrigerant, and this ordinarily presents no problem when the compressor is operating at or near its full capacity, since the flow of the lubricant laden compressor gas is at such a velocity that the lubricant does not become separated therefrom. However, when the compressor is operating at very low capacities, the entrained or occluded lubricant tends to become separated fromthe gaseous refrigerant, settling at the bottom of riser elements in the system. It is desirable that the lubricant be returned to the-compressor, and that it not become trapped at low points in the system, since it is possible that a slug of such lubricant could subsequently be carried along the system piping and enter the compressor to cause damage thereto on the compression stroke thereof. Moreover, it is desirable that the system be kept as free from such slugs of lubricant, since they tend to disturb the operation of the expansion valves located at the evaporator or evaporators.

of the system.

One of the principal objects of the invention is to provide a device which will return the lubricant of the system to the compressor, both when the compressor is up to full capacity and also when the demand thereon is extremely low.

Another object is to provide an integral return riser for a refrigeration system, which riser will increase the velocity of the refrigerant at reduced refrigeration loads,

I for the purpose of lifting the entrained lubricant vertically up the riser, which lubricant could otherwise collect at the low end of the riser and be prevented from returning to the compressor.

Still another object of the invention is to provide an integral lubricant return riser characterized by a pair of concentric tubes, the outer tube being closed at the bottom, and the inner concentric tube being spaced a small distance from the closed bottom of the outer tube, and providing a connection of the riser to the refrigeration system, and providing a pair of paths through the riser, one being of smaller cross sectional area providing rapid velocity to the refrigerant at periods of low demand upon the system, and providing a second path of larger cross sectional area for refrigerant when the system is operating at a larger demand, all to the end that the entrained lubricant will be returned to the compressor.

Other objects and important features of the invention will be apparent from a study of the specification following taken with the drawing which together describe and illustrate a preferred embodiment of the invention, and what is now considered to be the best mode of practising the principles thereof. Other embodiments may be suggested having the benefit of the teachings herein, and such other embodiments are intended to be reserved especially as they fall within the scope of the subjoined claims.

In the drawing: FIG. 1 is a view showing a conventional refrigeration Patented June 28,1966

system having the improved integral lubricant return riser embodied therein;

FIG. 2 is an enlarged elevational view of the integral lubricant return riser according to the present invention; and

FIG. 3 is a cross sectional view taken along the line 3-3 looking in the direction of the arrows showing details of structure for maintaining the tubes of the riser in concentric relationship.

Referring now to FIG. 1 of the drawing, there is shown a refrigeration system comprising a compressor 11 having the output therefrom connected by a line 11a to an integral lubricant return riser indicated generally by the reference numeral 10, it being connected by a line 10a to a'condenser 12 of the system. The condenser 12 is connected by a refrigerant line 13 to an evaporator 14, there being an expansion valve 16 interposed in line 13 between the condenser 12 and the evaporator 14 in the manner known in the art. The refrigerant which has been expanded in the evaporator 14 returns to the compressor 11 by a return line 17 connected to a similar integral lubricant riser 10 located between the evaporator 14 and the compressor 11, there being a return line 18 from such integral riser 10 back to the compressor 11.

The details of the integral lubricant return riser 10 are best seen with reference to FIGS. 2 and 3 in which figure details of the riser 10 connected at 11a to the output of the compressor 11 are shown. As seen in FIG. 2, the lubricant return riser 10 comprises an outer riser tube 19 connected to a T fitting 21, which in turn is connected to the line 11a. A short extension 22 having the same diameter or larger as the outer riser tube 19 expands below the T 21 and has the lower end thereof closed by a cap 23.

The outer riser tube 19 is concentric with an inner tube 24 of smaller diameter, and the bottom end of tube 24 is spaced adistance D approximately /3 the inside diameter of the tube 24.

The tubes 19 and 24 are maintained in spaced relationship by diametrically expanding pins 26 and 27 which are placed in position by drilling through the tubes 19 and 24, and brazing of the pins 26 and 27 where they extend through the outer tube 19 as at 28. As seen in FIGS. 2 and 3, the pins 26 and 27 are spaced a slight amount longitudinally along the two tubes 24 and 19, and

the complementary angle between the pins 26 and 27 is less" than 90", being of the order of from to such arrangement of the pins 26 and 27 preventing the concentric tubes from moving away from such concentricity. The paired pins 26 and 27 may be located convenient distances apart along the length of the concentric tubes.

24 and 19, for example, approximately a foot apart.

The concentric tubes 19 and 24 are selected in size so that an annular passageway 29 therebetween is much less than the cross sectional area of flow in tube 24.

creased, the velocity through the tube 24 is also decreased,

and it can no longer carry the entrained lubricant It thus settles out from the refrigerant, and collects in cap 23, eventually to rise to a point G to seal the lower end of the tube 24. The gaseous refrigerant entering T 21 creased flow in the riser 10 will cause an excessive pressure When the flow into the riser 10 by way of the line 11a is de.

drop along passageway 29. This increase in pressure difference forces the lubricant up through the lower end of tube 24 thereof, causing the trapped lubricant to be removed, at least in part, at the lower closed end of the riser 10.

From the description foregoing, it is believed evident that there has been provided some new and useful improvements in integral lubricant return risers which will insure the return of lubricant to the compressor during periods of large demand thereon, and for providing increased velocity through the riser when there are but low demands on the compressor.

The amount of lubricant trapped at the riser is quite minimal, not afiecting in any way the lubrication of the compressor. Moreover, when the compressor returns to higher output, the trapped lubricant in the riser is. returned back to the compressor.

Having thus described this invention in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains to make and use the same, and having set forth the best mode contemplated of carrying out this invention, the subject matter regarded as being patentable is particularly pointed out and distinctly claimed in what is claimed, it being understood that equivalents or modifications of, or substitutions for, parts of the above specifically described embodiment may be made without departing from the scope of the invention as set forth in what is claimed.

I claim:

1. In a refrigeration circuit including a compressor, a condenser and an evaporator and wherein lubricant from the compressor becomes mixed with the gaseous refrigerant and becomes difiicult to return with the refrigerant to the compressor in substantially vertical runs of said piping particularly during periods of reduced load on said compressor, means for increasing the velocity of the refrigerant gas at such reduced loads for lifting said gas and lubricant mixed therewith in such vertical run, said means comprising a pair of nested tubes, the outer of said tubes being a first connection to said circuit and being closed at the bottom, and the lower end of the inner tube being spaced from the lower closed end of the outer tube, the connection of said outer tube to said circuit being spaced above the lower ends of both of said tubes, a second circuit connection at the outer tube to the piping of said circuit, said second connection being located above the said first connection of the circuit to said outer tube, the inner tube being adapted to have its lower end sealed by lubricant separated from said refrigerant during reduced load, said inner and outer tubes having an annular passageway therebetween, which annular passageway alone is elfective to conduct lubricant laden refrigerant at high velocity during periods of reduced load by the sealing by lubricant of the lower end of said inner tube.

2. The invention according to claim 1 wherein said inner tube becomes unsealed by the velocity of the re frigerant at higher loads and both of said tubes are eifective to move lubricant laden refrigerant at high velocity.

3. The invention according to claim 1 wherein means are provided for maintaining said nested tubes in concentric relationship.

4. The invention according to claim 3 wherein said means comprises pins extending through the walls of said nested tubes, and wherein said pins have included complementary angles less than 5. An integral lubricant return riser for use in a re frigeration system Where the refrigerant becomes entrained with lubricant, said riser comprising a pair of substantially vertical nested tubes, the outer of said tubes being closed at the bottom and the lower end of the inner of said tubes being spaced a small distance above the closed lower end of the outer tube, an inlet and an outlet connection for said outer tube, said inlet connection to said outer tube being below the upper end thereof, and above the lower ends of said tubes, and said inlet and outlet being connected to said refrigeration system, the inner tube being adapted to have its lower end sealed by lubricant separated from said refrigerant when said system is at reduced load, said inner and outer tubes having an annular passageway there-between alone effective to conduct lubricant laden refrigerant at high velocity during periods of reduced load by the sealing by lubricant at the lower end of said inner tube.

6. The invention according to claim 5 wherein said inner tube becomes unsealed by the velocity of the refrigerant at higher loads and both of said tubes are effective to move lubricant laden refrigerant at high velocity.

7. The invention of claim 5 wherein means are provided for maintaining said nested tubes in concentric relationship.

8. The invention of claim 7 wherein said means comprises extending through the walls of said nested tubes, and wherein said pins have included angles less than 90".

References Cited by the Examiner UNITED STATES PATENTS 1,809,957 6/1931 Wright 62--47l 2,892,320 6/1959 Quick 6247l X 3,111,819 11/1963 Williams 6247l X ROBERT A. OLEARY, Primary Examiner.

W. E. WAYNER, Assistant Examiner. 

1. IN A REFRIGERATION CIRCUIT INCLUDING A COMPRESSOR, A CONDENSER AND AN EVAPORATOR AND WHEREIN LUBRICANT FROM THE COMPRESSOR BECOMES MIXED WITH THE GASEOUS REFRIGERANT AND BECOMES DIFFICULT TO RETUN WITH THE REFRIGERANT TO THE COMPRESSOR IN SUBSTANTIALLY VERTICAL RUNS OF SAID PIPING PARTICULARLY DURING PERIODS OF REDUCED LOAD ON SAID COMPRESSOR, MEANS FOR INCREASING THE VELOCITY OF THE REFRIGERANT GAS AT SUCH REDUCED LOADS FOR LIFTING SAID GAS AND LUBRICANT MIXED THEREWITH IN SUCH VERTICAL RUN, SAID MEANS COMPRISING A PAIR OF NESTED TUBES, THE OUTER OF SAID TUBES BEING A FIRST CONNECTION TO SAID CIRCUIT AND BEING CLOSED AT THE BOTTOM, AND THE LOWER END OF THE INNER TUBE BEING SPACED FROM THE LOWER CLOSED END OF THE OUTER TUBE, THE CONNECTION OF SAID OUTER TUBE TO SAID CIRCUIT BEING SPACED ABOVE THE LOWER ENDS OF BOTH OF SAID TUBES, A SECOND CIRCUIT CONNECTION AT THE OUTER TUBE TO THE PIPING OF SAID CIRCUIT, SAID SECOND CONNECTION BEING LOCATED ABOVE THE SAID FIRST CONNECTION OF THE CIRCUIT TO SAID OUTER TUBE, THE INNER TUBE BEING ADAPTED TO HAVE ITS LOWER END SEALED BY LUBRICANT SEPARATED FROM SAID REFRIGERANT DURING REDUCED LOAD, SAID INNER AND OUTER TUBES HAVING AN ANNULAR PASSAGEWAY THEREBETWEEN, WHICH ANNULAR PASSAGEWAY ALONE IS EFFECTIVE TO CONDUCT LUBRICANT LADEN REFRIGERANT AT HIGH VELOCITY DURING PERIODS OF REDUCED LOAD BY THE SEALING BY LUBRICANT OF THE LOWER END OF AID INNER TUBE. 